Allow for the duplication of sheets or sheet set up from sub categories. when creating a sheet, the sheet is given the next number in line from the last sheet created or modified, and placed in a ??? folder until you file it per the appropriate parameters. in more complicated projects, a sheet may require 3 or more categories to place the sheet in its rightful place in the project. If you could duplicate a sheet, you could copy everything from the titleblock to the filing parameters associated with the sheet that was duplicated.